In the flat-panel display devices of the related arts, the color display screen displays an image by means of pixel units. In general, a pixel unit includes sub-pixels with three different colors of red (R), green (G) and blue (B), and the color and brightness displayed in a pixel point (wherein each pixel point corresponds to one pixel unit) are controlled by means of controlling magnitudes of components of three RGB sub-pixels in corresponding pixel unit.
FIGS. 1A to 1C are structural schematic diagrams of arrangements of the RGB sub-pixels in a pixel unit in the related art, including the following three types of arrangement: bar-shape arrangement (see FIG. 1A), delta arrangement (see FIG. 1B) and mosaic arrangement (see FIG. 1C). In FIG. 1A, the RGB sub-pixels are arranged in rows sequentially and the same type of RGB sub-pixels are arranged in a column respectively. Since there is only one color in the direction of column in such an arrangement, the color nonuniformity and the error of color edge are readily to occur, affecting the display effect. In the arrangements of FIG. 1B and FIG. 1C, the color nonuniformity in some directions also occurs and the resolution therein is not high.
In practice, the resolution of a display device can be improved by increasing Pixels Per Inch (PPI) of the display device. In order to increase PPI, it is needed to reduce the area of each pixel as much as possible and to reduce the distance between pixels. Correspondingly, since each pixel consists of sub-pixels, the number of needed sub-pixels is large when a display device requires a large amount of pixels to achieve the display with high resolution. However, the improvement to the process will reach the limits with consistent refinement of the process.
Above all, the following technical problems usually occur in the display devices of the related art:
1) The actual display resolution of a display device is the same as the physical resolution thereof. To obtain higher display resolution, it is needed to improve the physical resolution of the display device by increasing the number of sub-pixels. As described above, it is difficult to further increase the resolution when the number of sub-pixels increases up to a certain amount, due to the limit of the improvement to the process;
2) The fact that the number of sub-pixels in a display device is large results in large number of data lines, and thus increases the power consumption of the display device and reduces the aperture ratio of the display device (Generally, the aperture ratio in the art refers to the ratio of the area of light-emitting region in the pixel region and the area of the repeatable pixel unit in the display region. The larger the aperture ratio is, the lower the required brightness of each pixel light-emitting region is and the lower the current density of the brightness of the light-emitting region is so as to achieve the same display brightness). When the resolution is high, it is hard to ensure the aperture ratio of sub-pixel, which may influence on the characteristics of the products, such as lifetime, brightness and the like, consequently.
3) The number of sub-pixels in the display device is large, and the area of each sub-pixel is small, which thus causes the manufacture process of the display device to have great difficulties and high cost. Take the organic light emission display (referred to as OLED) for example, in the related art of manufacturing top-emitting active matrix organic light emission diode (AMOLED), since the fine metal mask (referred to as FMM) usually has limitation to the minimum opening when used for evaporating the pixels arranged in parallel, the sub-pixels with different colors have limitations to the distance between the openings. Thereby, the manufacture process of the display device is inevitably limited to the area of openings of the fine metal mask and the precision of evaporation process, which causes the difficulty in implementing the display device with high resolution.
It can be seen that, how to implement the manufacture process for high-resolution pixels, to increase the aperture ratio of sub-pixels, to obtain good brightness level and to extend the lifetime in the meantime was always the urgent technical problems to be solved in the art.